Light emitting display panel and electronic device including the same

ABSTRACT

By controlling the optical thickness of the upper stacked structure disposed on the display panel, it is possible to periodically control the tristimulus value of Xr and the tristimulus value of Yg emitted from the electronic device. The optical thickness is determined by the thickness and refractive index of the upper stacked structure. This control may reduce the tristimulus value of Xr periodically or increase the tristimulus value of Yg periodically. The tristimulus value of Xr may be periodically decreased and the tristimulus value of Yg may be periodically increased at the same time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application is a divisional applicationof U.S. patent application Ser. No. 16/162,146 filed on Oct. 16, 2018,which claims priority under 35 USC § 119 to Korean Patent ApplicationNo. 10-2017-0177447, filed on Dec. 21, 2017, the entire contents ofwhich are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a light emitting display panel and anelectronic device, and more particularly to a light emitting displaypanel and an electronic device with improved display quality.

Electronic devices such as smart phones, tablets, notebook computers,navigations, and smart televisions are being developed. These electronicdevices have a display panel for providing information. Electronicdevices include a variety of electronic modules in addition to thedisplay panel.

Electronic devices should meet display quality requirements for theirintended use. The light generated from the light emitting element isemitted to the outside of the electronic device while generating variousoptical phenomena such as a resonance and interference. This opticalphenomenon may affect the quality of the displayed image.

SUMMARY

The present disclosure provides a display panel with improved displayquality.

The present disclosure also provides an electronic device with reducedreddishness of white images.

An embodiment of the inventive concept provides a light emitting displaypanel including: a base layer; a light emitting element including afirst electrode disposed on the base layer, a light emitting layerdisposed on the first electrode, and a second electrode disposed on thelight emitting layer; and a stacked structure disposed on the lightemitting element and including a plurality of layers, wherein a firstlayer to a q-th layer among the plurality of layers satisfy at least oneof the following Equations 1 and 2. The first layer contacts with thesecond electrode.

$\begin{matrix}{{{2\pi\; m} + \frac{2\pi}{3}} < {{2n_{1,z}d_{1}\sqrt{1 - {\frac{1}{n_{1}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + {2n_{2,2}d_{2}\sqrt{1 - {\frac{1}{n_{2}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}\mspace{14mu}\ldots\mspace{14mu} 2n_{q,z}d_{q}\sqrt{1 - {\frac{1}{n_{0}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + \phi_{1,{CE}} + \phi_{q,{q + 1}}} < {{2\pi\; m} + \frac{4\pi}{3}}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack \\{{{2\pi\; m} + \frac{5\pi}{3}} < {{2n_{1,z}d_{1}\sqrt{1 - {\frac{1}{n_{1}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + {2n_{2,2}d_{2}\sqrt{1 - {\frac{1}{n_{2}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}\mspace{14mu}\ldots\mspace{14mu} 2n_{q,z}d_{q}\sqrt{1 - {\frac{1}{n_{0}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + \phi_{1,{CE}} + \phi_{q,{q + 1}}} < {{2\pi\;( {m + 1} )} + \frac{\pi}{3}}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

In Equations 1 and 2, m is 0 and a natural number, n_(1,z) to n_(q,z)are refractive indices in a thickness direction of each of the firstlayer to the q-th layer, d₁ to d_(q) are respective thicknesses of thefirst layer to the q-th layer, θair is 20° to 40°, λ in Equation 1 is610 nm or more and 645 nm or less, and λ in Equation 2 is 515 nm or moreand 545 nm or less.

In Equations 1 and 2, ϕ_(1,CE) is the following Equation 3,

$\begin{matrix}{\phi_{1,{CE}} = {\tan^{- 1}( \frac{{Im}( r_{1,{CE}} )}{{Re}( r_{1,{CE}} )} )}} & \lbrack {{Equation}\mspace{14mu} 3} \rbrack\end{matrix}$

In Equation 3, r_(1,CE) is defined as a reflection coefficient of thefirst layer for the light emitting element, and if Im(r_(1,CE))≥0,0≤ϕ_(1,CE)≤π and if Im(r_(1,CE))<0, π<ϕ_(1,CE)<2π.

In Equations 1 and 2, if the refractive index of the q-th layer islarger than the refractive index of a q+1th layer, Φ_(q,q+1) is π and ifthe refractive index of the q-th layer is smaller than the refractiveindex of the q+1th layer, Φ_(q,q+1) is 0.

In an embodiment, the light emitting element may include a first lightemitting element for generating blue light having a peak in a range of440 nm to 460 nm; a second light emitting element for generating greenlight having a peak in a range of 515 nm to 545 nm; and a third lightemitting element for generating red light having a peak in a range of610 nm to 645 nm.

In an embodiment, the first layer to the q-th layer of the stackedstructure may satisfy Equation 4 below.n _(1,z) d ₁ +n _(2,z) d ₂ . . . n _(q,z) d _(q)≤4000 nm  [Equation 4]

In an embodiment, in Equation 4, q may be 3 to 5.

In an embodiment, the stacked structure may include a first organiclayer, a first inorganic layer, a second inorganic layer, a secondorganic layer, and a third inorganic layer, which are sequentiallystacked.

In an embodiment, the q-th layer may be the second inorganic layer.

In an embodiment, the first organic layer may include the same organicmaterial as the light emitting element, wherein the thicknesses of thefirst organic layer and the first inorganic layer may be 300 nm or less.

In an embodiment, the first inorganic layer may include lithiumfluoride.

In an embodiment, each of the second inorganic layer and the thirdinorganic layer may include at least one of silicon nitride, siliconoxynitride, silicon oxide, a titanium oxide layer, and aluminum oxide.

In an embodiment, a refractive index of the second inorganic layer maybe 1.5 to 1.9, and a thickness of the second inorganic layer may be 800nm to 2000 nm.

In an embodiment, a refractive index of the second organic layer may be1.4 to 1.8, and a thickness of the second organic layer may be 1000 nmto 12000 nm.

In an embodiment, the q-th layer may be the second organic layer.

In an embodiment, a refractive index of the second organic layer may be1.4 to 1.8, a thickness of the second organic layer may be 1000 nm to2500 nm, wherein a refractive index of the second inorganic layer may be1.5 to 1.9, and a thickness of the second inorganic layer may be 500 nmto 1600 nm.

In an embodiment, the stacked structure may include a first organiclayer disposed directly on the light emitting element, a first inorganiclayer disposed directly on the first organic layer, and an secondorganic layer and an second inorganic layer disposed on the firstinorganic layer, wherein the q-th layer may be the second organic layeror the second inorganic layer.

In an embodiment of the inventive concept, an electronic deviceincludes: a light emitting display panel; and a window disposed on thelight emitting display panel, wherein when the light emitting displaypanel displays a single white image, a graph showing an intensity oflight of the single white image measured at a height of 30 cm from thewindow and at a viewing angle of 20° to 40° in the CIE 1931 colorcoordinates is disposed on the left and top of a block body curve.

In an embodiment, the light emitting display panel may include: a firstlight emitting element configured to generate red light; a second lightemitting element configured to generate green light; a third lightemitting element configured to generate blue light; and interferencelayers disposed on the first light emitting element, the second lightemitting element, and the third light emitting element, wherein the redlight may be extinctively interfered in the interference layers, and theblue light may be constructively interfered in the interference layers.

In an embodiment, a first interference layer to a q-th interferencelayer (q is a natural number of 3 or more) among the interference layersmay satisfy at least one of Equation 1 and Equation 2 below. The firstinterference layer contacts with the first light emitting element, thesecond light emitting element, and the third light emitting element.

$\begin{matrix}{{{2\pi\; m} + \frac{2\pi}{3}} < {{2n_{1,z}d_{1}\sqrt{1 - {\frac{1}{n_{1}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + {2n_{2,2}d_{2}\sqrt{1 - {\frac{1}{n_{2}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}\mspace{14mu}\ldots\mspace{14mu} 2n_{q,z}d_{q}\sqrt{1 - {\frac{1}{n_{0}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + \phi_{1,{CE}} + \phi_{q,{q + 1}}} < {{2\pi\; m} + \frac{4\pi}{3}}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack \\{{{2\pi\; m} + \frac{5\pi}{3}} < {{2n_{1,z}d_{1}\sqrt{1 - {\frac{1}{n_{1}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + {2n_{2,2}d_{2}\sqrt{1 - {\frac{1}{n_{2}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}\mspace{14mu}\ldots\mspace{14mu} 2n_{q,z}d_{q}\sqrt{1 - {\frac{1}{n_{0}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + \phi_{1,{CE}} + \phi_{q,{q + 1}}} < {{2\pi\;( {m + 1} )} + \frac{\pi}{3}}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

In Equations 1 and 2, m is 0 and a natural number, n_(1,z) to n_(q,z)are refractive indices in a thickness direction of each of the firstlayer to the q-th layer, d₁ to d_(q) are respective thicknesses of thefirst layer to the q-th layer, θ_(air) is 20° to 40°, λ in Equation 1 is610 nm or more and 645 nm or less, and λ in Equation 2 is 515 nm or moreand 545 nm or less.

In Equations 1 and 2, Φ_(1,CE) is the following Equation 3,

$\begin{matrix}{\phi_{1,{CE}} = {\tan^{- 1}( \frac{{Im}( r_{1,{CE}} )}{{Re}( r_{1,{CE}} )} )}} & \lbrack {{Equation}\mspace{14mu} 3} \rbrack\end{matrix}$

In Equation 3, r_(1,CE) is defined as a reflection coefficient ofreflection coefficient for the light emitting element, and ifIm(r_(1,CE))≥0, 0≤ϕ_(1,CE)≤π and if Im(r_(1,CE))<0, π<Φ_(1,CE)<2π.

In Equations 1 and 2, if the refractive index of the q-th layer islarger than the refractive index of a layer disposed directly above theq-th layer, Φ_(q,q+1) is π and if the refractive index of the q-th layeris smaller than the refractive index of the layer disposed directlyabove the q-th layer, Φ_(q,q+1) is 0.

In an embodiment, a display surface where a single white image isdisplayed on the window may be defined by a first direction axis and asecond direction axis, wherein a length of the display surface along thefirst directional axis is 10 cm to 20 cm.

In an embodiment, the electronic device may further include at least oneof an input sensor and an anti-reflection layer disposed between thewindow and the light emitting display panel.

In an embodiment, the first interference layer to the q-th interferencelayer may satisfy Equation 4 below.n _(1,z) d ₁ +n _(2,z) d ₂ . . . n _(q,z) d _(q)≤4000 nm  [Equation 4]

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings are included to provide a furtherunderstanding of the inventive concept, and are incorporated in andconstitute a part of this specification. The drawings illustrateexemplary embodiments of the inventive concept and, together with thedescription, serve to explain principles of the inventive concept. Inthe drawings:

FIG. 1A is a perspective view of an electronic device according to anembodiment of the inventive concept;

FIG. 1B is a side view of an electronic device according to anembodiment of the inventive concept;

FIG. 2 is a graph showing optical characteristics of an electronicdevice according to a comparative example;

FIG. 3A is a graph showing optical characteristics of an electronicdevice according to an embodiment of the inventive concept;

FIG. 3B is a graph showing a change in the tristimulus value of Xraccording to the viewing angle of light emitted from an electronicdevice;

4A and 4B are cross-sectional views of an electronic device according toan embodiment of the inventive concept;

FIG. 5 is a plan view of a display panel according to an embodiment ofthe inventive concept;

FIG. 6A is an equivalent circuit diagram of a pixel according to anembodiment of the inventive concept;

FIG. 6B is a cross-sectional view of a display panel according to anembodiment of the inventive concept;

FIG. 6C is a graph showing the emission spectrum of the light generatedfrom a display panel according to an embodiment of the inventiveconcept;

FIGS. 7A, 7B, 7C and 7D are cross-sectional views showing a stackedstructure of display panels according to an embodiment of the inventiveconcept;

FIG. 8 is a graph showing a minimum perceptible color difference (MPCD)change according to an optical distance of a display panel according toan embodiment of the inventive concept;

FIG. 9 is a cross-sectional view showing the propagation path of lightgenerated from a display panel according to an embodiment of theinventive concept;

FIG. 10A is a cross-sectional view showing an optical interference pathfor a portion of an upper stacked structure according to an embodimentof the inventive concept;

FIG. 10B is a graph showing the interlayer reflectance of an upperstacked structure according to an embodiment of the inventive concept;and

FIG. 10C is a graph showing the interlayer phase change of an upperstacked structure according to an embodiment of the inventive concept.

DETAILED DESCRIPTION

Hereinafter, embodiments of the inventive concept will be described inmore detail with reference to the accompanying drawings. In thisspecification, when it is mentioned that a component (or, an area, alayer, a part, etc.) is referred to as being “on”, “connected to” or“combined to” another component, this means that the component may bedirectly on, connected to, or combined to the other component or a thirdcomponent therebetween may be present.

Like reference numerals refer to like elements. Additionally, in thedrawings, the thicknesses, proportions, and dimensions of components areexaggerated for effective description. “And/or” includes all of one ormore combinations defined by related components.

It will be understood that the terms “first” and “second” are usedherein to describe various components but these components should not belimited by these terms. The above terms are used only to distinguish onecomponent from another. For example, a first component may be referredto as a second component and vice versa without departing from the scopeof the present disclosure. The singular expressions include pluralexpressions unless the context clearly dictates otherwise.

In addition, terms such as “below”, “the lower side”, “on”, and “theupper side” are used to describe a relationship of configurations shownin the drawing. The terms are described as a relative concept based on adirection shown in the drawing.

In various embodiments of the inventive concept, the term “include,”“comprise,” “including,” or “comprising,” specifies a property, aregion, a fixed number, a step, a process, an element and/or a componentbut does not exclude other properties, regions, fixed numbers, steps,processes, elements and/or components.

FIG. 1A is a perspective view of an electronic device ED according to anembodiment of the inventive concept. FIG. 1B is a side view of anelectronic device ED according to an embodiment of the inventiveconcept. FIG. 2 is a graph showing optical characteristics of anelectronic device according to a comparative example. FIG. 3A is a graphshowing optical characteristics of an electronic device according to anembodiment of the inventive concept. FIG. 3B is a graph showing a changein the tristimulus value of Xr according to the viewing angle of lightemitted from an electronic device.

As shown in FIGS. 1A and 1B, the electronic device ED may display animage IM through a display surface ED-IS. The display surface ED-IS isparallel to the plane defined by the first directional axis DR1 and thesecond directional axis DR2. The normal direction of the display surfaceED-IS, that is, the thickness direction of the electronic device ED, isindicated by the third directional axis DR3.

When the direction in which the image is displayed is set to be the sameas the third direction axis DR3, an upper surface (or a front surface)and a lower surface (or a rear surface) of each of the elements aredefined by the third direction axis DR3. Hereinafter, the first to thirddirections refer to the same reference numerals as the directionsindicated by the first to third direction axes DR1, DR2, and DR3,respectively.

In an embodiment of the inventive concept, an electronic device EDhaving a planar display surface is shown, but is not limited thereto.The electronic device ED may further include a curved display surface.The electronic device ED may include a stereoscopic display surface. Thestereoscopic display surface includes a plurality of display areasindicating different directions, and may include, for example, apolygonal columnar display surface.

The electronic device ED according to this embodiment may be a rigiddisplay device. However, without being limited thereto, the electronicdevice ED according to the inventive concept may be a flexibleelectronic device ED having the shape of FIG. 1A in an unfolded state.In this embodiment, the electronic device ED applicable to a portableterminal is exemplarily shown. Although not shown in the drawing,electronic modules, camera modules, and power modules mounted on a mainboard may be arranged in a bracket/case together with an electronicdevice (ED) to constitute a mobile phone terminal.

As shown in FIGS. 1A and 1B, the display surface ED-IS includes adisplay area ED-DA in which an image IM is displayed and a non-displayarea ED-NDA adjacent to the display area ED-DA. The non-display areaED-NDA is an area where no image is displayed. FIG. 1A shows icon imagesas an example of an image IM. The non-display area ED-NDA is typicallythe bezel of an electronic device.

The display area ED-DA may have a rectangular form. The non-display areaED-NDA may surround the display area ED-DA. However, the inventiveconcept is not limited thereto, and the shape of the display area ED-DAand the shape of the non-display area ED-NDA may be relatively designed.For example, a non-display area ED-NDA may be disposed only in an areafacing in the first direction DR1.

As shown in FIGS. 1A and 1B, the viewing angles θ₀, θ₁, and θ₂ arechanged as a user looks at different positions of the electronic deviceED at a specific position. Depending on the viewing angle, a white imagedisplayed on the electronic device ED may look different to a userdepending on the viewing angles θ₀, θ₁, and θ₂. Here, the white imagemay be a background image or a single image displayed throughout thedisplay area ED-DA.

Since the light emitted from the display panel DP are provided to theuser differently depending on the viewing angles θ₀, θ₁, and θ₂. Thepropagation path of the light corresponding to the first viewing angleθ₀ and the propagation path of the light corresponding to the secondviewing angle θ₁ and the propagation path of the light corresponding tothe third viewing angle θ₂ are different from each other. In addition,the light generated in the inside of the display panel (for example, theorganic light emitting layer) passes through the plurality of layers andis emitted to the outside. Because the interference phenomenon by theplurality of layers varies depending on the propagation path of light,the white image displayed on the electronic device ED may look differentto a user depending on the viewing angles θ₀, θ₁, and θ₂.

The graphs described with reference to FIGS. 2 to 3B are based ontristimulus values of Xr, tristimulus values of Yg, and tristimulusvalues of Zb according to viewing angles. Xr is defined as the Xtristimulus value of the red component of the spectrum of light, Yg isdefined as the Y tristimulus value of the green component of thespectrum of light, and Zb is defined as the Z tristimulus value of theblue component of the spectrum of light. The graphs described below areshown in CIE 1931 color coordinates.

The graph shown in FIG. 2 shows the change in color tone according tothe viewing angle of a white image displayed on an electronic device ED.Factors affecting greatly to the color change of the white image are thetristimulus value of Xr for the red wavelength range, the tristimulusvalue of Yg for the blue wavelength range, and the tristimulus value ofZb for the blue wavelength range. These results may be expressed asfollows.WΔx=−0.0227+0.0934Xr+0.0196Yg−0.0917ZbWΔy=−0.00777+0.0337Xr+0.142Yg−0.167Zb

In Equations above, WΔx represents a displacement of white coloraccording to an x-axis and WΔy represents a displacement of white coloraccording to a y-axis.

The above relational expression means that a change in luminance in thered wavelength range, the blue wavelength range, and the blue wavelengthrange affects the color change of the white image. If the luminancechange in the red wavelength range, the blue wavelength range, and theblue wavelength range is controllable according to the viewing angle,the change in color tone according to the viewing angle of the whiteimage may be controlled.

Based on the spectra of light measured at different viewing angles at a30 cm height H1 from an electronic device ED, the tristimulus valueaccording to the viewing angle is calculated. A tristimulus value iscalculated from a spectrum of light using a color matching function, anda tristimulus value is normalized to calculate a color coordinate valueaccording to a viewing angle.

The measurement of the spectrum of the light emitted from the electronicdevice ED at the 30 cm height H1 (see FIG. 1B) reflects a conditionusing the portable terminal by the user.

The black body curve (BBC) shown in FIG. 2 corresponds to white. Thespectrum of light measured at a viewing angle of 0° (the first viewingangle θ₀ in FIG. 1) was set as a reference value. The spectrum of thelight corresponding to the reference value may be expressed by a colorcoordinate of (0, 0).

The first graph GH-R is the spectrum of the light emitted from theelectronic device according to the comparative example. According to thefirst graph GH-R, the color coordinates corresponding to the viewingangle of 20° to 40° are arranged on the lower or right side of the blackbody curve (BBC). Thus, when looking at a viewing angle of 20° to 40°,the white image displayed on the electronic device ED becomesreddish-white. In relation to the spectrum of the light measuredcorresponding to the viewing angle of 20° to 40°, a tristimulus value ofXr may be large or a tristimulus value of Yg may be small in comparisonto the black body curve (BBC).

For a white image displayed on an electronic device (ED, see FIG. 1B)with a length (L1, see FIG. 1B) of 10 cm to 20 cm, the image isrecognized as white at a 30 cm height H1 when viewed at a viewing angleof 0°. However, the image is recognized as a reddish white at a 30 cmheight H1 when viewed at a viewing angle of 20° to 40°.

A second graph GH-S in FIG. 3A is an analysis of the spectrum of lightemitted from an electronic device according to an embodiment of theinventive concept. According to the second graph GH-S, the colorcoordinates corresponding to the viewing angle of 20° to 40° arearranged on the upper or left side of the black body curve (BBC). Thus,when looking at a viewing angle of 20° to 40°, the white image is notrecognized as reddish-white.

Here, it may be seen that the color coordinates outside the range of 20°to 40° of the second graph GH-S do not change significantly with respectto the first graph GH-S. This is because, as will be described later, alayer having an optical distance of a predetermined thickness or more iscontrolled, and a layer having an optical distance of a predeterminedthickness or less is fixed to a constant thickness.

The first graph GH-RR shown in FIG. 3B shows the tristimulus valuechange of Xr according to the viewing angle of the electronic deviceaccording to the comparative example. The second graph GH-SR shown inFIG. 3B shows the tristimulus value change of Xr according to theviewing angle of the electronic device according to an embodiment of theinventive concept. The spectrum of the light emitted from the electronicdevice is measured according to the viewing angle, and the tristimulusvalue of Xr is calculated from the measured spectrum. According to thisembodiment, it may be seen that the tristimulus value of Xr in anembodiment of the inventive concept is decreased as compared with thecomparative example at a viewing angle of 20° to 40°. Also, it may beseen that the tristimulus value of the Xr outside the viewing anglerange of 20° to 40° of the second graph GH-SR is not significantlychanged with respect to the first graph GH-RR. In the embodiment of theinventive concept, it is possible to reduce the tristimulus value of Xrto prevent the reddish white image.

Unlike the embodiment described with reference to FIGS. 3A and 3B, in anembodiment of the inventive concept, the tristimulus value of Yg may beincreased to prevent the reddish white image. On the other hand, sincethe tristimulus value of Zb increases or decreases along the black bodycurve, the effect on the reddish white image of the tristimulus value ofZb is not significant.

According to the inventive concept, by controlling the material and thethickness of the upper stacked structure disposed on the display panel,the tristimulus value of Xr and the tristimulus value of Yg of the lightemitted from an electronic device may be periodically controlled. Thiscontrol may reduce the tristimulus value of Xr periodically or increasethe tristimulus value of Yg periodically. The tristimulus value of Xrmay be periodically decreased and the tristimulus value of Yg may beperiodically increased at the same time. Hereinafter, the upper stackedstructure and the optical distance will be described in more detail withreference to FIGS. 4A to 10.

4A and 4B are cross-sectional views of an electronic device ED accordingto an embodiment of the inventive concept. FIG. 5 is a plan view of adisplay panel DP according to an embodiment of the inventive concept.FIG. 6A is an equivalent circuit diagram of a pixel PX according to anembodiment of the inventive concept. FIG. 6B is a cross-sectional viewof a display panel DP according to an embodiment of the inventiveconcept. FIG. 6C is a graph showing the emission spectrum of the lightgenerated from the display panel DP according to an embodiment of theinventive concept.

An electronic device ED according to an embodiment of the inventiveconcept may include a display panel DP, an input sensor ISU, ananti-reflector RPU, and a window WU. The display panel DP generates animage, and the input sensor ISU acquires coordinate information of anexternal input (e.g., a touch event). The anti-reflector RPU reduces thereflectance of light incident from the outside, and the window WUprovides the display surface ED-IS. At least some of the configurationsof the display panel DP, the input sensor ISU, the anti-reflector RPUand the window WU are formed by a continuous process, or at least someconfigurations may be coupled together via an adhesive member.

FIGS. 4A and 4B illustrate a pressure sensitive adhesive film (PSA) asan adhesive member. The adhesive member described below may includeconventional adhesives or gluing agents and is not particularly limited.In an embodiment of the inventive concept, the anti-reflector RPU may bereplaced with another configuration or omitted. In an embodiment of theinventive concept, the input sensor ISU may be omitted.

Referring to FIG. 4A, the display panel DP according to an embodiment ofthe inventive concept may be a light-emitting type display panel. Forexample, the display panel DP may be an organic light emitting displaypanel or a quantum dot light emitting display panel. The light emittinglayer of the organic light emitting display panel may include an organiclight emitting material. The light emitting layer of the quantum dotlight emitting display panel may include quantum dot, quantum rod, andthe like. Hereinafter, the display panel DP is described as an organiclight emitting display panel.

The input sensor ISU may include at least one conductive layer and atleast one insulating layer. At least one conductive layer may include aplurality of sensor electrodes. The input sensor ISU may include aplurality of sensor electrodes, such as capacitive touch panels.

The anti-reflector RPU reduces the reflectance of natural light (orsunlight) incident from above the window WU. The anti-reflector RPUaccording to an embodiment of the inventive concept may include aretarder and a polarizer. The retarder may be a film type or a liquidcrystal coating type, and may include a λ/2 retarder and/or a λ/4retarder. The polarizer may also be of film type or liquid crystalcoating type. The film type includes a stretch-type synthetic resinfilm, and the liquid crystal coating type may include liquid crystalsarranged in a predetermined arrangement. The retarder and the polarizermay further include a protective film. The retarder and the polarizeritself or the protective film may be defined as the base layer of theanti-reflector RPU.

The anti-reflector RPU according to an embodiment of the inventiveconcept may include color filters. The color filters have apredetermined arrangement. The arrangement of the color filters may bedetermined in consideration of the light emission colors of the pixelsincluded in the display panel DP. The anti-reflector RPU may furtherinclude a black matrix disposed adjacent to the color filters.

The window WU according to an embodiment of the inventive conceptincludes a base layer WP-BS and a light blocking pattern WP-BZ. The baselayer WP-BS may include a glass substrate and/or a synthetic resin filmor the like. The base layer WP-BS is not limited to a single layer. Thebase layer WP-BS may include two or more films bonded with an adhesivemember.

The light blocking pattern WP-BZ partially overlaps the base layerWP-BS. The light blocking pattern WP-BZ may be disposed on the backsurface of the base layer WP-BS to define a bezel area of the displaydevice DD, that is, a non-display area DD-NDA (see FIG. 1A).

The light blocking pattern WP-BZ may be formed as a colored organicfilm, for example, by a coating method. Although not shown separately,the window WU may further include a functional coating layer disposed onthe front surface of the base layer WP-BS. The functional coating layermay include an anti-fingerprint layer, anti-reflective layer, and a hardcoating layer.

The input sensor ISU, the anti-reflector RPU, and the window WU shown inFIG. 4A may have a panel shape and coupled to one another using anadhesive member. According to the inventive concept, the input sensorISU, the anti-reflector RPU, and the window WU are not limited to apanel shape. The input sensor ISU, the anti-reflector RPU, and thewindow WU according to an embodiment of the inventive concept may havemulti-layer structure sequentially disposed on the base.

The multi-layer structure is formed through a series of processes withdifferent configurations. In other words, the lowest layer of themulti-layer structure is disposed on the base. The base may beseparately provided or the display panel DP may be the base. FIG. 4Billustrates an electronic device including an input sensing layer ISLexemplarily. The lowest layer of the input sensing layer ISL, forexample, an insulating layer or a conductive layer, may be directlydisposed on the uppermost layer (base surface) of the display panel DP.

As shown in FIG. 5A, the display panel DP includes a driving circuitGDC, a plurality of signal lines SGL (hereinafter referred to as signallines), a plurality of signal pads DP-PD (hereinafter referred to assignal pads), and a plurality of pixels PX-R, PX-G, and PX-B(hereinafter referred to as pixels). The driving circuit GDC may includea scan driving circuit. The signal lines SGL may include scan lines GL,data lines DL, a power line PL, and a control signal line CSL. Thecontrol signal line CSL may provide control signals to a scan drivingcircuit. The signal pads DP-PD are connected to corresponding signallines among the signal lines SGL. The signal pads DP-PD may be connectedto a circuit board not shown.

The display panel DP may include a pixel region DP-DA and a peripheralregion DP-NDA on a plane. The pixel region DP-DA is a region wherepixels PX-R, PX-G, and PX-B are arranged and the peripheral regionDP-NDA is a region where no pixels PX-R, PX-G, and PX-B are arranged.The pixel region DP-DA and the peripheral region DP-NDA correspond tothe display area ED-DA and the non-display area ED-NDA shown in FIG. 1A,but are not necessarily limited thereto.

Each of the pixels PX-R, PX-G, and PX-B includes an organic lightemitting diode and a pixel driving circuit connected thereto. The pixelsPX-R, PX-G, and PX-B may be divided into a plurality of groups accordingto the emitted color. The pixels PX-R, PX-G and PX-B may include, forexample, red pixels PX-R, green pixels PX-G, and blue pixels PX-B. Thepixels PX-R, PX-G, and PX-B may include organic light emitting layers ofdifferent materials.

FIG. 6A shows one pixel PX of the pixels PX-R, PX-G, and PX-B shown inFIG. 5. The organic light emitting diode OLED may be afront-light-emitting-type diode or a rear-light-emitting-type diode. Thepixel PX includes a first transistor T1 (or a switching transistor), asecond transistor T2 (or a driving transistor), and a capacitor Cst as apixel driving circuit for driving the organic light emitting diode OLED.The first power voltage ELVDD is supplied to the second transistor T2and the second power voltage ELVSS is supplied to the organic lightemitting diode OLED. The second power voltage ELVSS may be lower thanthe first power voltage ELVDD.

The first transistor T1 outputs a data signal applied to the data lineDL in response to a scan signal applied to the scan line GL. Thecapacitor Cst charges a voltage corresponding to a data signal receivedfrom the first transistor T1. The second transistor T2 is connected tothe organic light emitting diode OLED. The second transistor T2 controlsa driving current flowing through the organic light emitting diode OLEDin correspondence to a charge amount stored in the capacitor Cst.

The equivalent circuit is only an embodiment and is not limited thereto.The pixel PX may further include a plurality of transistors, and mayinclude a larger number of capacitors. The organic light emitting diodeOLED may be connected between the power line PL and the second powervoltage ELVSS.

As shown in FIG. 6B, a circuit element layer DS-CL and a display elementlayer DS-OLED are sequentially arranged on the base substrate DS-G. Inthis embodiment, the circuit element layer DS-CL may include a pluralityof insulating layers. The plurality of insulating layers may include abuffer film BFL, a first inorganic film 10, a second inorganic film 20,and an organic film 30. The material of the inorganic film and theorganic film is not particularly limited, and in an embodiment of theinventive concept, the buffer film BFL may be omitted.

The first transistor T1 and the second transistor T2 may be disposed onthe buffer film BFL. On the other hand, according to another embodimentof the inventive concept, some of the first transistor T1 and the secondtransistor T2 may be modified as a bottom gate structure.

A pixel defining film PDL and an organic light emitting diode OLED maybe disposed on the organic film 30. The pixel defining film PDL mayinclude an organic material. A first electrode AE is disposed on theorganic film 30. The first electrode AE is connected to the outputelectrode of the second transistor T2 through a through hole penetratingthe organic film 30. An opening part OP is defined in the pixel definingfilm PDL. The opening part OP of the pixel defining film PDL exposes atleast a part of the first electrode AE. In an embodiment of theinventive concept, the pixel defining film PDL may be omitted.

A hole control layer HCL, a light emitting layer EML, an electroncontrol layer ECL, and a second electrode CE may be sequentiallyarranged on the first electrode AE. The hole control layer HCL mayinclude a hole transport layer. The hole control layer HCL may furtherinclude a hole injection layer disposed between the hole transport layerand the first electrode AE. The electron control layer ECL may includean electron transport layer. The electron control layer ECL may furtherinclude an electron injection layer disposed between the electrontransport layer and the second electrode CE. The second electrode CE mayinclude silver (Ag), magnesium (Mg), aluminum (Al), and nickel (Ni).

An upper stacked structure UIL is disposed on the second electrode CE.The upper stacked structure UIL contains a plurality of insulatinglayers. The plurality of insulating layers may be divided into aplurality of groups according to their functions. A detailed descriptionof the upper stacked structure UIL will be given later.

FIG. 6C shows emission spectra of light generated from the organic lightemitting diodes of the red pixel PX-R, the green pixel PX-G, and theblue pixel PX-B. The Y axis represents the emission intensity and theemission intensities of the first graph L-B, the second graph L-G, andthe third graph L-R are not related to each other.

As shown in the first graph L-B, the first light generated in the bluepixel PX-B has a peak in the first central wavelength range. Here, thecentral wavelength range is defined as the range in which the peakwavelength may be arranged. The first light may have a wavelength of atleast 410 nm or more and 480 nm or less, and the first centralwavelength range may be 440 nm or more and 460 nm or less. As shown inthe second graph L-G, the second light generated in the green pixel PX-Ghas a peak in the second central wavelength range. The second light mayhave a wavelength of at least 500 nm or more and 570 nm or less, and thesecond central wavelength range may be 515 nm or more and 545 nm orless. As shown in the third graph L-B, the third light generated in thered pixel PX-R has a peak in the third central wavelength range. Thethird light may have a wavelength of at least 580 nm or more and 675 nmor less, and the second central wavelength range may be 610 nm or moreand 645 nm or less.

FIGS. 7A to 7D are cross-sectional views showing a stacked structure ofthe display panels DP according to an embodiment of the inventiveconcept. FIG. 8 is a graph showing a minimum perceptible colordifference (MPCD) change according to an optical distance of a displaypanel according to an embodiment of the inventive concept. FIGS. 7A to7D show an organic light emitting diode OLED and an upper stackedstructure UIL disposed on the organic light emitting diode OLED in asimplified way.

As shown in FIGS. 7A to 7D, the upper stacked structure UIL includes aplurality of layers. The layers of the upper stacked structure UIL aredisposed adjacent to the organic light emitting diode OLED to cause aninterference in the light emitted from the organic light emitting diodeOLED. As shown in the second graph GH-S in FIG. 3A, the reason that thecolor coordinates measured at a viewing angle of 20° to 40° are arrangedon the upper side or the left side of the black body curve is becausethe upper stacked structure UIL satisfies a specific condition describedlater.

The “specific condition” may be determined by the optical distance ofthe layers (hereinafter referred to as interference layers) disposedbetween the reference layers of the plurality of layers from the secondelectrode CE. The optical distance of a single layer is defined as theproduct of the refractive index of a single layer and the thickness of asingle layer. The optical distance of a structure including a pluralityof layers is defined as the sum of the optical distances of theplurality of layers.

As shown in FIG. 8, since the layers disposed farther than the opticaldistance 4000 nm from the upper surface of the second electrode CE arearranged farther than the interference distance of the organic lightemitting diode OLED, thus, interference effect is low and does notaffect the change of tristimulus value. Therefore, the reference layeris a layer in which the upper surface is disposed within an opticaldistance of 4000 nm from the upper surface of the second electrode CEand may be determined as an interference layer disposed on the uppermostone of the above-described interference layers.

That is, the interference layers satisfy the following equations.n_(1,z) is the refractive index in the thickness direction of the firstinterference layer with respect to the peak wavelength. d1 is thethickness of the first interference layer. n_(q,z) is the refractiveindex in the thickness direction of the reference layer with respect tothe peak wavelength. dq is the thickness of the reference layer.n _(1,z) d ₁ +n _(2,z) d ₂ . . . n _(q,z) d _(q)≤4000 nm

As shown in FIGS. 7A to 7D, the upper stacked structure UIL may includea first protective layer CPL, a second protective layer PCL, and anencapsulation layer TFE. The upper stacked structure UIL may furtherinclude layers other than the above layers, or some of the layers may beomitted.

The first protective layer CPL prevents damage to the second electrodeCE from subsequent processes, for example, a plasma process. The firstprotective layer CPL may include an organic material. The firstprotective layer CPL may include, for example, a hole transport materialcalled HT01. In addition, the first protective layer CPL may includeother organic materials used in the organic light emitting diode OLEDdescribed with reference to FIG. 6B. The refractive index of the firstprotective layer CPL may be 1.5 to 2.2, and the thickness may be 45 nmto 120 nm.

The second protective layer PCL prevents damage to the first protectivelayer CPL, which is an organic layer, from the subsequent chemical vapordeposition process of the inorganic material. The second protectivelayer PCL may be formed by a sputtering method which is a physical vapordeposition method. The second protective layer PCL may include, forexample, LIF. The refractive index of the second protective layer PCLmay be 1.3 to 2.2, and the thickness may be 10 nm to 50 nm.

The encapsulation layer TFE seals the organic light emitting diode OLED.The encapsulation layer TFE may include at least one inorganic film(hereinafter referred to as a sealing inorganic film) and at least oneorganic film (hereinafter referred to as a sealing organic film).

The sealing inorganic film protects the organic light emitting diodeOLED from moisture/oxygen, and the sealing organic film protects theorganic light emitting diode OLED from foreign substances such as dustparticles. The sealing organic film may include a silicon nitride layer,a silicon oxynitride layer, and a silicon oxide layer, a titanium oxidelayer, or an aluminum oxide layer and is not limited thereto. Thescaling organic film may include an acrylic based organic film and isnot particularly limited. The sealing inorganic film and the sealingorganic film may be formed by a deposition method, and in particular,the sealing organic film may be formed by depositing an acrylic monomer.

FIG. 7A shows an encapsulation layer TFE in which a first sealinginorganic film IOL1, a sealing organic film OL, and a second sealinginorganic film IOL2 are sequentially stacked. FIG. 7B shows anencapsulation layer TFE in which a sealing organic film OL and a sealinginorganic film IOL are sequentially stacked. FIG. 7C shows anencapsulation layer TFE in which a sealing inorganic film IOL and asealing organic film OL are sequentially stacked. FIG. 7D show aencapsulation layer TFE in which a first sealing inorganic film IOL1 asealing organic film OL and a second sealing inorganic film IOL2 aresequentially stacked.

In the upper stacked structure UM shown in FIG. 7A, the reference layerRL may be the first sealing inorganic film IOL1. Here, the refractiveindex of the first sealing inorganic film IOL1 may be 1.5 to 1.9, andthe thickness may be 800 nm to 2000 nm. The refractive index of thesealing organic film OL may be 1.4 to 1.8, and the thickness may be 1000nm to 12000 nm. The refractive index of the second sealing inorganicfilm IOL2 may be 1.5 to 1.9, and the thickness may be 800 nm to 2000 nm.

Since the thickness of the first protective layer CPL and the secondprotective layer PCL is relatively thin, the reference layer RL isdetermined by the stacked structure of the encapsulation layer TFE. InFIG. 7A, the first sealing inorganic film IOL1 having an upper surfacearranged at an optical distance of 4000 nm from the upper surface of thesecond electrode CE is determined as a reference layer RL.

In the upper stacked structure UIL shown in FIG. 7B, the reference layerRL may be a sealing organic film OL. The refractive index of the sealingorganic film OL may be 1.4 to 1.8, and the thickness may be 1000 nm to3000 nm. The sealing inorganic film IOL may be formed undersubstantially the same conditions as the second sealing inorganic filmIOL2 of FIG. 7A.

In the upper stacked structure UIL shown in FIG. 7C, the reference layerRL may be a sealing organic film OL. The refractive index of the sealingorganic film OL may be 1.4 to 1.8, and the thickness may be 1000 nm to2500 nm. In this case, the sealing inorganic film IOL may have arefractive index of 1.5 to 1.9 and a thickness of 500 nm to 1600 nm.

FIGS. 7B and 7C illustrate the upper stacked structure UIL in which thesealing organic film OL is the reference layer RL. However, in anembodiment of the inventive concept, a sealing inorganic film IOL may bethe reference layer RL. At this time, the sealing organic film OL has arelatively thin thickness and the sealing inorganic film IOL has arelatively large thickness.

In the upper stacked structure UIL shown in FIG. 7D, the reference layerRL may be a sealing organic film OL. The refractive index of the sealingorganic film OL may be 1.4 to 1.8, and the thickness may be 1000 nm to2000 nm. At this time, the first sealing inorganic film IOL1 may bethinner than the first sealing inorganic film IOL1 of FIG. 7A. Therefractive index of the first sealing inorganic film IOL1 may be 1.5 to1.9, and the thickness may be 500 nm to 1600 nm. The second sealinginorganic film IOL2 may be formed under the same conditions as thesecond sealing inorganic film IOL2 of FIG. 7A. The refractive index ofthe second sealing inorganic film IOL2 may be 1.5 to 1.9, and thethickness may be 800 nm to 2000 nm.

FIG. 9 is a cross-sectional view showing the propagation path of lightgenerated from a display panel DP according to an embodiment of theinventive concept. FIG. 10A is a cross-sectional view showing an opticalinterference path for a portion of an upper stacked structure UILaccording to an embodiment of the inventive concept. FIG. 10B is a graphshowing the interlayer reflectance of an upper stacked structure UILaccording to an embodiment of the inventive concept. FIG. 10C is a graphshowing the interlayer phase change of an upper stacked structure UILaccording to an embodiment of the inventive concept. Below, withreference to FIGS. 9 to 10C, the influence of the interference layersfrom the second electrode CE to the reference layer on the tristimulusvalue of light measured at a viewing angle of 20° to 40° will bedescribed in more detail.

FIG. 9 shows a path through which light generated in a light emittinglayer EML is emitted from an electronic device ED. The electronic deviceED shown in FIG. 4A is shown as an example. According to thisembodiment, the electronic device ED includes a panel shaped inputsensor ISU, and defines the upper surface of the base layer WP-BS of thewindow WU as the uppermost surface of the electronic device ED. Inaddition, the input sensor ISU also includes one inorganic layer IOL-Iand one conductive layer CP-I. This embodiment is described based on theelectronic device ED including the upper stacked structure UIL shown inFIG. 7A. The first protective layer CPL, the second protective layerPCL, and the first sealing inorganic film IOL1 are shown in FIG. 9 asthe fourth layer CPL, the fifth layer PCL and the sixth layer IOL1.

According to Equations 1 to 3, as the value of the spectral intensityLe, increases, the tristimulus value of Xr, the tristimulus value of Yg,and the tristimulus value of Zb increase.Xr=∫ _(λ) L _(e,Ω,λ)(λ) x (λ)dλ  Equation 1Yg=∫ _(λ) L _(e,Ω,λ)(λ) y (λ)dλ  Equation 2Zb=∫ _(λ) L _(e,Ω,λ)(λ) z (λ)dλ  Equation 3

According to the following paper “Simulation of light emission fromthin-film microcavities”, Kristiaan A. Neyts, J. Opt. Soc. Am. A/Vol.15, No. 4/April 1998”, the intensity K value of light passing through aplurality of layers may be determined by Equation 4 below. The K valuein Equation 4 may be substantially equal to the value of L_(e, Ω, λ) inEquations 1 to 3.

$\begin{matrix}{K = {{const}\mspace{14mu}{{Re}\lbrack {\frac{\beta^{2}}{K_{e}^{3}K_{z,e}}\frac{( {1 \pm \alpha_{+}} )( {1 \pm \alpha_{-}} )}{( {1 - \alpha} )}} \rbrack}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

The intensity of light passing through n layers (where n is a naturalnumber of 3 or more) expressed by Equation 4 may be applied to theintensity of light (ED-L, hereinafter referred to as external emissionlight) emitted from the electronic device ED in FIG. 9. This is becauselight (EML-L, hereinafter referred to as source light) generated in thelight emitting layer EML-L passes through the plurality of layers, thatis, the hole control layer HCL to the base layer WP-BS.

Equation 4 may be separated as shown in Equation 5 below to checkinterference effects of the i-th layer to the nth layer among the nlayers.

On the other hand, the equations described herein are calculated undertransverse-magnetic (TM) polarization conditions. The TM polarizationconditions satisfy the following relationship.

$r_{j{({j + 1})}} = \frac{\frac{k_{z,j}}{m_{j}^{2}} - \frac{k_{z,{j + 1}}}{n_{j + 1}^{2}}}{\frac{k_{z,j}}{m_{j}^{2}} + \frac{k_{z,{j + 1}}}{n_{j + 1}^{2}}}$

In Equation 5, K ‘represents the intensity of light incident on the i-thlayer. Here, the light emitting layer is the first layer (i=1).

$\begin{matrix}{K = {K^{\prime}\frac{k_{{i + 1},z}}{k_{i,z}}\frac{{{t_{i{({i + 1})}}e^{i({k_{i,z}d_{i}})}}}^{2}}{{( {1 - {r_{{(i)}i}r_{{(i)}{({i + 1})}}e^{2{i{({k_{i,z}d_{i}})}}}}} )}^{2}} \times \frac{k_{{i + 2},z}}{k_{{i + 1},z}}\frac{{{t_{{({i + 1})}{({i + 1})}}e^{i({k_{{i + 1},z}d_{i + 1}})}}}^{2}}{{( {1 - {r_{{({j + 1})}t}r_{{({i + 1})}{({i + 2})}}e^{2{i{({k_{{i - 1},z}d_{i + 1}})}}}}} )}^{2}}\mspace{14mu}\ldots \times \frac{k_{{air},z}}{k_{n,z}}\frac{{{t_{n{({n + 1})}}e^{i{({k_{N,z}d_{N}})}}}}^{2}}{{( {1 - {r_{Nt}r_{Nar}e^{2{i{({k_{N,z}d_{N}})}}}}} )}^{2}}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

Equation 6 is the result of summarizing in correspondence with i=4 inEquation 5.

$\begin{matrix}{K = {K^{\prime}\frac{{{t_{45}t_{56}\mspace{14mu}\ldots\mspace{14mu} t_{{({n - 1})}n}t_{n{({n - 1})}}e^{i{({{k_{4,z}d_{4}} + k_{5,z} + \ldots + {k_{N - {1z}}d_{N - 1}} + {k_{N,z}d_{N}}})}}}}^{2}}{\begin{matrix}{{( {1 - {r_{4t}r_{45}e^{2{ik}_{4,z}d_{4}}}} )( {1 - {r_{5t}r_{56}e^{2{ik}_{5,z}d_{5}}}} )\mspace{14mu}\ldots}} \\{{( {1 - {r_{{({N - 1})}t}r_{{({N - 1})}N}e^{2{i{({k_{{N - 1},z}d_{N - 1}})}}}}} )( {1 - {r_{Nt}r_{Nair}e^{2{i{({k_{N,z}d_{N}})}}}}} )}}^{2}\end{matrix}}\frac{k_{{air},z}}{k_{4,z}}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

In Equation 6, d4 to d6, and do represent the thickness of each layer.r(i, i+1) represents the reflection coefficient between the i-th layerand the (i+1)th layer. r(i,t) represents the reflection coefficientbetween the i-th layer and the layers disposed below the i-th layer.

The denominator of Equation 6 is given by Equation 7 below.

$\begin{matrix}\begin{matrix}{{( {1 - {r_{4t}r_{45}e^{2{ik}_{4,z}d_{4}}}} )( {1 - {r_{5t}r_{56}e^{2{ik}_{5,z}d_{5}}}} )\mspace{14mu}\ldots}} \\{{{( {1 - {r_{{({N - 1})}t}r_{{({N - 1})}N}e^{2{i{({k_{{N - 1},z}d_{N - 1}})}}}}} )( {1 - {r_{Nt}r_{Nair}e^{2{i{({k_{N,z}d_{N}})}}}}} )}}^{2}K_{2,z}}\end{matrix} & {{Equation}\mspace{14mu} 7}\end{matrix}$

The denominator may be interpreted as the product of the bracketarguments. The bracket arguments are related to a plurality of layers,respectively. The influence of the fourth layer CPL to the sixth layerIOL1 on the intensity K of the external emission light may be expressedby Equation 8.

$\begin{matrix}{{( {1 - {r_{4t}r_{45}e^{2{ik}_{4,z}d_{4}}}} )( {1 - {r_{5t}r_{56}e^{2{i{({k_{5,z}d_{5}})}}}}} )( {1 - {r_{6t}r_{67}e^{i{({k_{6,z}d_{6}})}}}} )}} & {{Equation}\mspace{14mu} 8}\end{matrix}$

Equation 8 is solved to obtain the following Equation 9. Equation 8 isdeveloped using the following relational expression.

$\begin{matrix}{\mspace{79mu}{{r_{{({i + 1})}t} = \frac{r_{{({i + 1})}i} - {r_{it}e^{2{ik}_{i,z}d_{i}}}}{1 - {r_{it}r_{i{({i + 1})}}e^{2{ik}_{i,z}d_{i}}}}}{1 - {r_{4t}r_{45}e^{2{ik}_{4,z}d_{4}}} - {r_{54}r_{56}e^{2{ik}_{5,z}d_{5}}} - {r_{65}r_{67}e^{2{ik}_{6,z}d_{6}}} - {r_{4t}r_{56}e^{{2{ik}_{4,z}d_{4}} + {2{ik}_{5,z}d_{5}}}} - {r_{54}r_{67}e^{{2{ik}_{5,z}d_{5}} + {2{ik}_{6,z}d_{6}}}} - {r_{4t}r_{67}e^{{2{ik}_{4,z}d_{4}} + {2{ik}_{5,z}d_{5}} + {2{ik}_{6,z}d_{6}}}}}}} & {{Equation}\mspace{14mu} 9}\end{matrix}$

The six arguments excluding 1 in Equation 9 represent six interferenceoccurring in the fourth layer CPL to the sixth layer IOL1 as shown inFIG. 10A. The first of the six arguments corresponds to the firstinterference path LP4 of FIG. 10A, the second argument corresponds tothe second interference path LP5 of FIG. 10A, the third argumentcorresponds to the third interference path LP6 of FIG. 10A, the fourthargument corresponds to the fourth interference path LP4-5 of FIG. 10A,the fifth argument corresponds to the fifth interference path LP5-6 ofFIG. 10A, and the sixth argument corresponds to the sixth interferencepath LP4-6 of FIG. 10A.

The denominator of Equation 6 may be adjusted by controlling sixarguments. When the denominator value of Equation 6 is decreased, theintensity K of the external emission light is increased, and when thedenominator value is increased, the intensity value K of the externalemission light is decreased.

Of the six interference paths, the sixth interference path LP4-6 is setas the main argument. In the second interference path LP5, the thirdinterference path LP6, and the fifth interference path LP5-6 may beneglected because the reflection coefficient between the adjacent layersis small, thus, resonance occurs weakly.

In FIG. 10B, the first graph G34 shows the reflectance between the thirdlayer CE and the fourth layer CPL, the second graph G45 shows thereflectance between the fourth layer CPL and the fifth layer PCL, thethird graph G56 shows the reflectance between the fifth layer PCL andthe sixth layer IOL1, and the fourth graph G67 shows the reflectancebetween the sixth layer IOL1 and the seventh layer OL.

The reflection coefficient between adjacent layers in the firstinterference path LP4 and the fourth interference path LP4-5 isrelatively large. However, the fourth layer CPL and the fifth layer PCLwhich are thinner than the thickness of the sixth layer IOL1 do notaffect a light efficiency and an optical characteristic much. However,the light efficiency and the 45° optical characteristic are affected bychanges in the thicknesses of the fourth layer CPL and the fifth layerPCL. For example, in the second graph GH-S shown in FIG. 3A, in ordernot to significantly change the color coordinates outside the viewingangle range of 20° to 40°, the factors corresponding to the firstinterference path LP4 and the fourth interference path LP4-5 are fixed,and the intensity K of the external emission light is controlled byadjusting only the sixth factor corresponding to the sixth interferencepath LP4-6.

Here, the relatively thin thickness range of the fourth layer CPL andthe fifth layer PCL may be equal to or more than 10 nm and equal to orless than 300 nm. The sixth argument of Equation 9 may be expressed asEquation 10 below.

$\begin{matrix}{{r_{4t}r_{67}e^{2{i{({{k_{4,z}d_{4}} + {k_{5,z}d_{5}} + {k_{6,z}d_{6}}})}}}} = {{r_{4t}}e^{i\;\phi_{4,t}}{r_{67}}e^{i\;\phi_{6,7}}e^{2{i{({{k_{4,z}d_{4}} + {k_{5,z}d_{5}} + {k_{6,z}d_{6}}})}}}}} & {{Equation}\mspace{14mu} 10}\end{matrix}$

Equation 10 represents separately the phase which is an argumentaffecting the interference. In FIG. 10C, the first graph G34 shows thephase change of the light reflecting the interface between the thirdlayer CE and the fourth layer CPL, the second graph G45 shows the phasechange of the light reflecting the interface between the fourth layerCPL and the fifth layer PCL, the third graph G56 shows the phase changeof the light reflecting the interface between the fifth layer PCL andthe sixth layer IOL1, and the fourth graph G67 shows the phase change ofthe light reflecting the interface between the sixth layer IOL1 and theseventh layer OL. As in the first graph G34, the phase of light passingthrough the interface between the third layer CE and the fourth layerCPL is changed depending on the wavelength of light.

As a result, Equation 6 may be expressed as Equation 11.

$\begin{matrix}{K = {K^{\prime}\frac{\begin{matrix}{{t_{23}t_{34}\mspace{14mu}\ldots\mspace{14mu} t_{{({n - 1})}n}t_{n{({n + 1})}}}} \\{e^{i{({{k_{2,z}d_{2}} + {k_{3,z}d_{3}} + \ldots + {k_{{n - 1},z}d_{n - 1}} + {k_{n,z}d_{n}}})}}}^{2}\end{matrix}}{\begin{matrix}{{1 - \ldots - {{r_{4t}}{r_{67}}e^{{{2{i{({{k_{4,z}d_{4}} + {k_{5,z}d_{5}} + {k_{6,z}d_{6}}})}}} + {i\;\phi_{4,t}} + {i\;{\phi 6}}},7}\mspace{14mu}\cdots}}} \\{{{r_{N{({N - 1})}}}{r_{N{({N + 1})}}}e^{2{i{({k_{N,z}d_{N}})}}}}}^{2}\end{matrix}\mspace{14mu}}\frac{k_{{air},z}}{k_{2,z}}}} & {{Equation}\mspace{14mu} 11}\end{matrix}$

When Equation 11 is changed to a cosine value and the absolute value issolved, Equation 12 as follows.

$\begin{matrix}{K = {K^{\prime}\frac{\begin{matrix}{{t_{23}t_{34}\mspace{14mu}\ldots\mspace{11mu} t_{{({n - 1})}n}t_{n{({n + 1})}}}} \\{e^{i{({{k_{2,z}d_{2}} + {k_{3,z}d_{3}} + \ldots + {k_{{n - 1},z}d_{n - 1}} + {k_{n,z}d_{n}}})}}}^{2}\end{matrix}}{\begin{matrix}{1 - \ldots - {2{r_{4t}}{r_{67}}}} \\{{\cos( {{2( {{k_{4,z}d_{4}} + {k_{5,z}d_{5}} + {k_{6,z}d_{6}}} )} + \phi_{4,t} + \phi_{6,7}} )} +} \\{4{r_{4t}}^{2}{r_{67}}^{2}\mspace{11mu}\ldots}\end{matrix}}\frac{k_{{air},z}}{k_{2,z}}}} & {{Equation}\mspace{14mu} 12}\end{matrix}$

In Equation 12, the cosine function of the denominator is as follows.cos(2(k _(4,z) d ₄ +k _(5,z) d ₅ +k _(6,z) d ₆)+ϕ_(4,t)+ϕ_(6,7))

The intensity K value of the external emission light expressed byEquation 12 may be increased or decreased by the bracket argument of thecosine function. That is, the tristimulus value of Xr, the tristimulusvalue of Yg, and the tristimulus value of Zb may be increased ordecreased by the bracket argument of the cosine function.

The cosine function may be generalized as Equation 13 below.cos(2(k _(1,z) d ₁ +k _(2,z) d ₂ . . . +k _(q,z) d_(q))+ϕ_(1,CE)+ϕ_(q,q+1))  Equation 13

In Equation 12, the fourth layer CPL is expressed by the first layer inEquation 13, and the first layer is a layer contacting the upper surfaceof the second electrode CE. A plurality of layers are sequentiallystacked from the first layer to the q-th layer. The q-th layercorresponds to the above-mentioned reference layer.

If the value of Equation 13 cos(2(k_(1,z)d₁+d₂ . . .k_(q,z)d_(q))+ϕ_(1,CE)+ϕ_(q,q+1)) is 0, 2π, 4π . . . , the intensity Kof the external emission light expressed by Equation 12 increases. Thatis, constructive interference occurs in the stacked structure from thefirst layer to the q-th layer.

If the value of Equation 13 cos(2(k_(1,z)d₁+k_(2,z)d₂ . . .+k_(q,z)d_(q))+ϕ_(1,CE)+ϕ_(q,q+1)) is π, 3π . . . , the intensity Kvalue of the external emission light expressed by Equation 12 increases.That is, destructive interference occurs in the stacked structure fromthe first layer to the q-th layer.

As shown in FIG. 3A, in order for the first graph GH-R to change likethe second graph GH-S, the tristimulus value of Xr should be decreasedor the tristimulus value of Yg should be increased. Alternatively, bothtwo conditions should be satisfied.

In order to reduce the tristimulus value of Xr, the intensity of theexternal light, that is, the K value, should be decreased, and thebracket arguments of Equation 13 should satisfy Equation 14 below.

$\begin{matrix}{{{{2\pi\; m} + \frac{2\pi}{3}} < {{2k_{1,z}d_{1}} + {2k_{2,z}d_{2}\mspace{14mu}\ldots} + {2k_{q,z}d_{q}} + \phi_{1,{CE}} + \phi_{q,{q + 1}}}},{< {{2\pi\; m} + \frac{4\pi}{3}}}} & {{Equation}\mspace{14mu} 14}\end{matrix}$

Here, m may be 0, 1, 2, . . . . d1 to dp are the thickness argument ofeach layer, for example, d1 is the thickness of the first layer. InEquation 14, k_(i, z) are expressed by Equation 15 below.

$\begin{matrix}{k_{i,z} = {\sqrt{n_{i}^{2} - {\sin^{2}\mspace{14mu}\theta_{air}}}\frac{2\pi}{\lambda}}} & {{Equation}\mspace{14mu} 15}\end{matrix}$

Equation 14 may be expressed as Equation 16 using Equation 15.

$\begin{matrix}{{{2\pi\; m} + \frac{2\pi}{3}} < {{2n_{1,z}d_{1}\sqrt{1 - {\frac{1}{n_{1}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + {2n_{2,z}d_{2}\sqrt{1 - {\frac{1}{n_{2}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}\mspace{14mu}\ldots\mspace{14mu} 2n_{q,z}d_{q}\sqrt{1 - {\frac{1}{n_{q}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + \phi_{1,{CE}} + \phi_{q,{q + 1}}} < {{2\pi\; m} + \frac{4\pi}{3}}} & {{Equation}\mspace{14mu} 16}\end{matrix}$

θair may be an emission angle θ of the external emission light ED-Lshown in FIG. 9, which may be the viewing angle shown in FIG. 1B. θairmay be 20° to 40°. Especially, θair may be 30°. λ is the peak wavelengthof the light incident on the first layer. Herein, n_(1,z) is therefractive index in the thickness direction of the first layer withrespect to the peak wavelength.

In Equations 14 and 16, Φ_(1,CE) are as shown in the following Equation17.

$\begin{matrix}{\phi_{1,{CE}} = {\tan^{- 1}( \frac{{Im}( r_{1,{CE}} )}{{Re}( r_{1,{CR}} )} )}} & \lbrack {{Equation}\mspace{14mu} 17} \rbrack\end{matrix}$

Here, r_(1,CE) represent the reflection coefficients of the organiclight emitting diode OLED of the first layer, that is, the layercontacting the upper surface of the second electrode CE. In other words,it represents the reflection coefficient for the structure from thefirst electrode AE of the layer contacting the upper surface of thesecond electrode CE to the second electrode CE. Therefore, Φ_(1,CE) maybe determined according to the refractive indices of the secondelectrode CE and the first electrode AE, and the thicknesses andrefractive indices of the layers disposed between the second electrodeCE and the first electrode AE. r_(1,CE) may contain imaginary values andreal values. When Im(r_(1,CE))≥0, the conditions of 0≤Φ_(1,CE)≤π aresatisfied and when Im(r_(1,CE))<0, the conditions of π<Φ_(1,CE)<2π aresatisfied.

If the refractive index of the q-th layer (or reference layer) isgreater than the refractive index of the (q+1) th layer, Φ_(q,q+1) areπ, and If the refractive index of the q-th layer (or reference layer) issmaller than the refractive index of the (q+1)-th layer, Φ_(q,q+1) are0.

The tristimulus value of Xr may be reduced by destructively interferingwith the light generated from the red pixel PX-R. Therefore, λ may be610 nm or more and 645 nm or less.

In order to reduce the tristimulus value of Yg, the intensity of theexternal emission light, that is, the K value, should be increased, andEquation 18 should be satisfied. The arguments of Equation 18 are thesame as those of Equation 16.

$\begin{matrix}{{{2\pi\; m} + \frac{5\pi}{3}} < {{2n_{1,z}d_{1}\sqrt{1 - {\frac{1}{n_{1}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + {2n_{2,z}d_{2}\sqrt{1 - {\frac{1}{n_{2}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}\mspace{14mu}\ldots\mspace{11mu} 2n_{q,z}d_{q}\sqrt{1 - {\frac{1}{n_{q}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + \phi_{1,{CE}} + \phi_{q,{q + 1}}} < {{2{\pi( {m + 1} )}} + \frac{\pi}{3}}} & {{Equation}\mspace{14mu} 18}\end{matrix}$

The tristimulus value of Yg may be increased by constructivelyinterfering with the light generated from the blue pixel PX-B.Therefore, λ may be 515 nm or more and 545 nm or less.

Equations 16 and 18 may be satisfied to reduce the tristimulus value ofXr and increase the tristimulus value of Yg. In such a way, thetristimulus value of Xr of the light emitted from the electronic devicemay be reduced to prevent the reddish phenomenon of the white image. Thetristimulus value of Yg of the light emitted from the electronic devicemay be increased to prevent the reddish phenomenon of the white image.

According to the above description, when the characteristics of lightmeasured at a viewing angle of 20° to 40° are displayed in colorcoordinates, the coordinates are arranged on the left side or the upperside of the black body curve. The tristimulus value of Xr of the lightemitted from the electronic device may be reduced to prevent the reddishphenomenon of the white image. The tristimulus value of Yg of the lightemitted from the electronic device may be increased to prevent thereddish phenomenon of the white image.

Although the exemplary embodiments of the inventive concept have beendescribed, it is understood that the inventive concept should not belimited to these exemplary embodiments but various changes andmodifications can be made by one ordinary skilled in the art within thespirit and scope of the inventive concept as hereinafter claimed.

What is claimed is:
 1. A light emitting display panel comprising: a baselayer; a light emitting element including a first electrode disposed onthe base layer, a light emitting layer disposed on the first electrode,and a second electrode disposed on the light emitting layer; and astacked structure disposed on the light emitting element and including aplurality of layers, wherein a first layer to a q-th layer among theplurality of layers satisfy at least one of the following Equations 1and 2, the first layer contacts with the second electrode,$\begin{matrix}{{{2\pi\; m} + \frac{2\pi}{3}} < {{2n_{1,z}d_{1}\sqrt{1 - {\frac{1}{n_{1}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + {2n_{2,z}d_{2}\sqrt{1 - {\frac{1}{n_{2}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}\mspace{14mu}\ldots\mspace{14mu} 2n_{q,z}d_{q}\sqrt{1 - {\frac{1}{n_{q}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + \phi_{1,{CE}} + \phi_{q,{q + 1}}} < {{2\pi\; m} + \frac{4\pi}{3}}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack \\{{{2\pi\; m} + \frac{5\pi}{3}} < {{2n_{1,z}d_{1}\sqrt{1 - {\frac{1}{n_{1}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + {2n_{2,z}d_{2}\sqrt{1 - {\frac{1}{n_{2}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}\mspace{14mu}\ldots\mspace{14mu} 2n_{q,z}d_{q}\sqrt{1 - {\frac{1}{n_{q}^{2}}\sin^{2}\theta_{air}}}\frac{2\pi}{\lambda}} + \phi_{1,{CE}} + \phi_{q,{q + 1}}} < {{2{\pi( {m + 1} )}} + \frac{\pi}{3}}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$ in Equations 1 and 2, m is 0 and a natural number, n1,z tonq,z are refractive indices in a thickness direction of each of thefirst layer to the q-th layer, d1 to dq are respective thicknesses ofthe first layer to the q-th layer, θair is 20° to 40°, λ in Equation 1is 610 nm or more and 645 nm or less, and λ in Equation 2 is 515 nm ormore and 545 nm or less, in Equations 1 and 2, Φ1,CE is the followingEquation 3, $\begin{matrix}{{\phi_{1,{CE}} = {\tan^{- 1}( \frac{{Im}( r_{1,{CE}} )}{{Re}( r_{1,{CR}} )} )}},} & \lbrack {{Equation}\mspace{14mu} 3} \rbrack\end{matrix}$ in Equation 3, r1,CE is defined as a reflectioncoefficient of the first layer for the light emitting element, and ifIm(r1,CE)≥0, 0≤ϕ1,CE≤π and if Im(r1,CE)<0, π<ϕ1,CE<2π, and in Equations1 and 2, if the refractive index of the q-th layer is larger than therefractive index of a q+1th layer, Φq,q+1 is π and if the refractiveindex of the q-th layer is smaller than the refractive index of theq+1th layer, Φq,q+1 is
 0. 2. The light emitting display panel of claim1, wherein the light emitting element comprises a first light emittingelement for generating blue light having a peak in a range of 440 nm to460 nm; a second light emitting element for generating green lighthaving a peak in a range of 515 nm to 545 nm; and a third light emittingelement for generating red light having a peak in a range of 610 nm to645 nm.
 3. The light emitting display panel of claim 1, wherein thefirst layer to the q-th layer of the stacked structure satisfy Equation4 below,n _(1,z) +d ₁ +n _(2,z) d ₂ . . . n _(q,z) d _(q)≤4000 nm.  [Equation 4]4. The light emitting display panel of claim 3, wherein in Equation 4, qis 3 to
 5. 5. The light emitting display panel of claim 1, wherein thestacked structure comprises a first organic layer, a first inorganiclayer, a second inorganic layer, a second organic layer, and a thirdinorganic layer, which are sequentially stacked.
 6. The light emittingdisplay panel of claim 5, wherein the q-th layer is the second inorganiclayer.
 7. The light emitting display panel of claim 6, wherein the firstorganic layer comprises the same organic material as the light emittingelement, wherein the thicknesses of the first organic layer and thefirst inorganic layer are 300 nm or less.
 8. The light emitting displaypanel of claim 7, wherein the first inorganic layer comprises lithiumfluoride.
 9. The light emitting display panel of claim 6, wherein eachof the second inorganic layer and the third inorganic layer comprises atleast one of silicon nitride, silicon oxynitride, silicon oxide, atitanium oxide layer, and aluminum oxide.
 10. The light emitting displaypanel of claim 6, wherein a refractive index of the second inorganiclayer is 1.5 to 1.9, and a thickness of the second inorganic layer is800 nm to 2000 nm.
 11. The light emitting display panel of claim 6,wherein a refractive index of the second organic layer is 1.4 to 1.8,and a thickness of the second organic layer is 1000 nm to 12000 nm. 12.The light emitting display panel of claim 5, wherein the q-th layer isthe second organic layer.
 13. The light emitting display panel of claim12, wherein a refractive index of the second organic layer is 1.4 to1.8, a thickness of the second organic layer is 1000 nm to 2500 nm,wherein a refractive index of the second inorganic layer is 1.5 to 1.9,and a thickness of the second inorganic layer is 500 nm to 1600 nm. 14.The light emitting display panel of claim 1, wherein the stackedstructure comprises a first organic layer disposed directly on the lightemitting element, a first inorganic layer disposed directly on the firstorganic layer, and an second organic layer and an second inorganic layerdisposed on the first inorganic layer, wherein the q-th layer is thesecond organic layer or the second inorganic layer.